rc dosen’t really support fisheye lenses.
but you can have a go using division. I’ve had a few goes with a 10.5mm and some worked, and some crashed. but i wont really bother trying again until rc gets updated. it was a bit hit or miss, and generally introduced more issues than it was worth. esp mixing normal photos with fisheye.
fisheye images with the scans should be fine if you colour them before they are imported to rc.
rc is matching by colour, so it really is needed. otherwise you could have a go with control points and see if that helps.